ON A NEW SPECIES OF OPHIURELLA. 57 



by a kind of ball and socket joint ; 3rd, the basal or ventral plates 

 which close the ray below are small and much concealed, they 

 likewise carry many short, stout spines. One of the spiniferous 

 arms of the Ophiurella as it lies on the slab of calcareous grit 

 before me, resembles, a marine worm, the Nereis nuntia, and hence 

 the origin of the specific name I have ventured to give this 

 new Brittle-star. The arms are very much bent and curled, so 

 that this species may be said to have had highly moveable 

 arms. 



Dimensions. Diameter of the disk six-tenths of an inch ; 

 length of an arm, two inches and six tenths. This is less than 

 in the living state, as none of the arms are preserved up to their 

 terminations. 



Affinities and Differences. The fragmentary condition of the 

 disk prevents any definite conclusions as to the true generic 

 position of this form, but it agrees with Ophiurella closer than 

 with any other. It has the small disk with the upper and under 

 surfaces covered with fine granules ; the arms long, compressed 

 and flattened, the lateral and ventral plates supporting spines, 

 which are specially jointed to the lateral plates. In all these 

 essential generic characters it agrees with Ophiurella. I know 

 of no figured species from the corallian rocks that resembles the 

 Brittle-star. The only form that occurs to my mind is Ophiurella 

 bispinosa, d'Orb, which has only been named, but was neither 

 described nor figured by the author. Our species is so widely 

 different from all the others, that there can be no confusion with 

 them. 



Locality and Stratigraphical Position. This Brittle-star was 

 obtained by Professor Buckman, F.GKS., from the calciferous 

 grit at Sandsfoot Castle, near Weymouth, who kindly sent the 

 specimen to me for a description of the species as a contribution 

 to the " Proceedings of the Dorset Natural History and Anti- 

 quarian Field Club," a request which I willingly comply with, 

 hoping that the members of the youngest among the naturalists' 

 field clubs may make many additions of new species from the 

 rocks which lie within the area of its operations. 



